The present invention relates to a flexible conduit for transporting abrasive slurry, comprising a flexible tubular body, such as a rubber tube, and a plurality of wear-resistant rings provided in the body along the length of the conduit for protecting the inner surface of the body against abrasive action of the slurry. This abrasive action may include abrasion, erosion and cutting of sharp edges of pieces of e.g. rock.
U.S. Pat. No. 4,537,224 A relates to a rubber tube for dredging work embedded in and used in a pipe-line used for dredging work in the sea or river. This rubber tube has a tubular body made of rubber having a plurality of strengthening clothes embedded therein, and a plurality of metal rings axially arranged in a suitably spaced relation which are embedded in an inner peripheral surface of said tubular body and which inner peripheral surface forms a part of the inner peripheral surface of said tubular body. The metal rings have their joined surface with the tubular body placed in parallel to the axis and axial both ends thereof made thin in wall-thickness. Thereby, a contact area between the metal ring and the tubular body is increased to strengthen a bonding force and minimize a peeling off of the joined surface between both ends of the metal rings and the tubular body. A wire 30 is tightened between annular ribs 32 and 33 (FIG. 5). The bonding between the metal rings 26 and the rubber tube is strengthened by these annular ribs 32, 33 in connection with compressive force acting axially on the rubber tube 21. There is a need for a rubber tube wherein bonding between the metal ring and the tubular body is improved in radial direction rather than the axial direction.
DE8437910 relates to a rubber hose with a hose wall wherein the metal rings are embedded which metal rings overlap in axial direction of the hose. The metal rings do not have any indentation. The metal rings seem not wear resistant itself since the metal rings are embedded in a rubber layer and have for their purpose to enable the hose to withstand high external pressure.
Such a flexible conduit for transporting abrasive slurry is known from GB 1573189 A which relates to a reinforced rubber hose primarily for use with slurry or a bulky solid in liquid.
A dredge hoses, which is a flexible conduit for transporting abrasive slurry, is inside particularly sensitive to wear when slurry with sharp particles is transported. For that reason the elastomeric wear layer in the hose is provided with metal wear rings. These metal wear rings are adhered or vulcanized into the elastomeric wear layer. Rubber hoses used in suction and pressure lines for dredgers are subject to a considerable amount of wear as the material conveyed there-through cuts the inner wall. To counteract such damage, hoses are known with an internal wear and incision resisting layer of rubber of a thickness of 50 mm or above, or overlapping inserts of conical shape are secured by screw means passing through the wall of the hose are used. The thick layer of rubber is often destroyed in a short time and the lining of steel inserts is expensive and only effective with suction hoses.
This invention of GB 1573189 A seeks to provide a rubber hose for use in conveying bulky and angular solids and which can be subject to suction or pressure and therefore provides a reinforced rubber hose with an inner wall comprising a layer of rubber in which metal insert bodies are embedded the inserts each being of a width substantially equal to the width of the layer of rubber and lying in or immediately beneath the surface of the inner wall, a reinforcement being provided over said layer with an outer cover over the reinforcement. The inserts are firmly embedded in the layer of rubber, and are preferably in the form of annular rings or helical coils extending along the length of the hose. The inserts are resistant to the action of the substance being conveyed and therefore to some extent prevent same from penetrating the rubber to any appreciable depth. On the other hand, the longitudinal spaces between adjacent inserts are completely filled with a resistant rubber and are sufficiently wide to ensure that the hose will retain flexibility. These required spaces to obtain an acceptable flexibility however do result in according unprotected areas of the hose wherein still abrasive particles may penetrate to a certain depth.
In addition EP 1 877 689 B1 relates to a flexible pipe for transporting abrasive slurry, comprising a tubular body of a flexible polymer, such as rubber, and a multitude of coaxial, wear-resistant rings provided in the polymer along the length of the tube, which rings and which tubular body have substantially the same internal diameter. The wear-resistant rings function to slow down the wearing process, for example by preventing sharp objects in the slurry cutting through the rubber wearing layer over a large distance. Said rings are usually formed of steel plate, cut, rolled and welded. Common kinds of steel are used, but also high-tensile and wear-resistant kinds, such as Creusabro™ and Hardox™.
The object of the invention of EP 1 877 689 B1 is to provide a flexible pipe which is more resistant to wear and damage. Therefore, the thickness of the rings near their inner circumference is to that end smaller over at least part of their circumference than the thickness of the rings near their outer circumference. Various properties of the pipe can be improved by using this configuration of the rings, such as the bending radius, the life and the stiffness. In particular the anchoring of the rings in the pipe is improved in this manner. However, the thickness of the rings near their inner circumference being smaller does result in an increase of unprotected area of the hose wherein still abrasive particles may penetrate to a certain depth. In addition, flexibility of the flexible pipe is less controllable during the operational life of the flexible pipe because the amount of rubber between adjacent rings keeps on changing during life of the flexible pipe.
In general the metal rings used in known dredge hoses are hardened or cast iron, produced in different cross sections. When these known rings break, parts thereof easily break out of the body. These broken out parts then flow with the slurry and may damage a downstream apparatus. In addition, the hose will worn out faster without complete wear rings.